Wireless communications networks, such as cellular networks, need to support integrated multimedia applications with various quality of service (QoS) requirements. By differentiating the QoS for different high-speed services, it becomes possible to support multimedia demands for a variety of user equipment (UE) in a cell served by a base station. The UE can include cellular telephones, mobile computing devices, and other end-user terminals.
Due to differences between traffic characteristics of data packet services and traditional circuit-switched voice services, dedicated channels are allocated for data services in many systems and many standard specifications are known, such as the High Data Rate (HDR) systems, see Bender, et al. “CDMA/HDR: A bandwidth efficient high speed data service for nonadic users,” IEEE Commun. Mag., Vol. 38, No. 7, pp. 70-77, July, 2000, the 1xTREME of 3rd Generation Partnership Project 2 (3GPP2), Motorola and Nokia, “3GPP2 1xTREME Presentation,” C00-20000327-003, March, 2000, and the High Speed Downlink Packet Access (HSDPA) of 3rd Generation Partnership Project (3GPP), Motorola, “Feasibility study of advanced technique for High Speed Downlink PacketAccess,” TSG-R WG1 document, R1-556, April, 2000.
In a wireless packet network, the high-speed downlink data channel is shared by multiple UE within the same cell. Many new technologies have been developed for the shared downlink channel by standardization organizations. For example, in HSDPA of 3GPP, solutions include adaptive modulation and coding (AMC), hybrid automatic repeat request (H-ARQ), fast cell selection (FCS), and multiple-input-multiple-output (MIMO) systems.
AMC provides a link adaptation method that match the modulation-coding scheme to conditions of the channel for each user. In a system with AMC, UE close to the base station is typically assigned higher order modulation with higher code rates, e.g., 64 QAM with R=¾ turbo codes. The modulation-order and/or the code rate decrease as the distance between the UE and the base station increases.
H-ARQ provides a retransmission mechanism for lost or erroneous packets. There are many schemes for implementing H-ARQ, such as chase combining, rate compatible punctured turbo codes, and incremental redundancy.
With FCS, the UE selects the ‘best’ cell that should be used for the downlink channel through uplink signaling. Thus, while multiple cells can be members of an active set, only one cell transmits at any one time, potentially decreasing interference and increasing system capacity.
Multiple-input-multiple-output (MIMO) systems employ multiple antennas at both the transmitter of the base station and the receiver of the UE. This provides several advantages over conventional single antenna systems and transmit diversity techniques that only have multiple antennas at the transmitter.
An important issue is how to integrate resource control and management with these new technologies. For example, the data transmission capacity at a base station will vary according to the dynamic changing of AMC schemes. Given the same amount of code and time space, and resources, UE with a higher modulation scheme can usually obtain a higher data rate than UE with a lower modulation scheme.
Of particular concern to the present invention is resource allocation with QoS control for high-speed downlink shared channel adapted for AMC and H-ARQ systems.
Packet scheduling is one of the most important QoS control approaches for wireless multimedia networks. A large number of packet scheduling techniques are known for wireless networks, for example, channel state dependent packet scheduling (CSDPS), Fragouli et al., “Controlled multimedia wireless link sharing via enhanced class-based queuing with channel-state dependent packet scheduling,” Proc. IN-FOCOM'98, vol. 2, pp. 572-580, March 1998, idealized wireless fair queuing process (IWFQ), see Lu et al., “Fair scheduling in wireless packet net-works,” IEEE/ACM Trans. Networking, Vol. 7, No. 4, pp. 473-489, 1999, channel-condition independent fair queuing (CIF-Q), Ng et al., “Packet fair queuing algorithms for wireless networks with location-dependent errors,” Proc. INFOCOM98, pp. 1103-1111, March 1998, server based fairness (SBFA), Ramanathan et al., “Adapting packet fair queuing algorithms to wireless networks,” Proc. ACM MOBICOM'98, October 1998, improved channel state dependent packet scheduling (I-CSDPS), Gomez et al., “The Havana frame-work for supporting application and channel dependent QoS in wireless networks,” Proc. ICNP'99, pp. 235-244, November 1999, channel adaptive fair queuing (CAFQ), Wang et al., “Channel Capacity Fair Queuing in Wireless Networks: Issues and A New Algorithm,” ICC 2002, April 2002, modified largest weighted delay first (M-LWDF), Andrews et al., “Providing quality of service over a shared wireless link,” IEEE Communications Magazine, Vol. 39, No. 2, pp. 150-154, February 2001, and code-division generalized processor sharing (CDGPS), Xu et al., “Dynamic bandwidth allocation with fair scheduling for WCDMA systems,” IEEE Wireless Communications, April 2002.
Except for Wang, Andrews, and Xu, most prior art approaches assume a simple wireless model, such as two-state Markov model. A scheduler simulates an error-free system running a wireline packet scheduling process when sessions have ‘good’ channel states, i.e., the effective throughput is at a maximum. When the session that is scheduled to transmit data encounters a ‘bad’ channel state, the session gives up a transmit opportunity to other error-free sessions, e.g., those with good channel states. Then, these error-free sessions give their transmit rights back to the error session in compensation, when the channel state is good again. Those processes mainly provide fairness and a ‘soft’ QoS guarantees.
Wang describes a new definition of fairness, and a scheduling process adapting to several channel conditions. However, explicit QoS guarantees are not provided. Andrews describes a user scheduling process based on a tradeoff between delay and throughput. That approach assumes that each UE can only support one QoS traffic class at a time. Xu applies generalized processor sharing (GPS) scheme dynamically to spreading codes rather than to time slots for different UE.
It is desired to provide a method and system for dynamically controlling resources in a high-speed down link channel. The method and system should be closely integrated with other HSDPA technologies, such as AMC and H-ARQ. Because the AMC changes dynamically according to the channel conditions, the scheduler mechanism should not be based on the simple prior art ‘on/off’ wireless channel model.
In addition, H-ARQ introduces extra traffic load into wireless networks. Prior art scheduling techniques do not consider the increased load.
Furthermore, it is important to distinguish between original packets and retransmitted packets, and UE should be able to receive multiple streams with different QoS requirements simultaneously.
For instance, a user should be able to view a streaming video from a video server, while downloading a text file from a FTP server. Thus, the scheduler at the base station needs to handle both QoS traffic classes and different UEs sharing the capacity of the same downlink HSDPA channel.
Usually, prior art solutions only schedule resources to different UE terminals on an individual basis, without considering the resource and QoS requirements of different traffic classes.
Therefore, there is a need for a dynamic resource control system and method that considers all network traffic so that the throughput of the entire network is optimized.